The present invention relates to the improvement of high-power laser systems employed for example in telemetry, plasma physics or thermonuclear fusion, without this list being intended to be limitating.
Power laser systems usually comprise one or more amplifying elements in which a beam of increasing intensity is propagated, one thereof forming the oscillator.
Owing to the conditions at the limits (diaphragm, edge of the amplifiers) and imperfections in these media, an even perfect beam (plane or spherical wave) becomes deformed and rather rapidly has small-scale intensity fluctuations the transverse dimensions of which may be small with respect to the diameter of the beam.
These small-scale intensity fluctuations considerably limit the overall energy contained in the beam since they are subject in all the transparent media and consequently in the amplifiers, to a self-focussing effect. Moreover, in the case of solid systems this self-focussing effect produces a localized deterioration of the amplifying media and this is the cause of irreversible damage. It is also known that this effect becomes more rapid as the transverse dimension of the small-scale intensity fluctuations decreases (see for example the article by R. Y. Chiao, E. Garmire and C. H. Townes, Physical Review Letters, 13, 479 (1964).
In the oscillators the energy density is still higher and there is a danger that the electro-optical systems, the mirrors and other elements will be damaged.
The presence of these small-scale intensity fluctuations consequently considerably decreases the acceptable limit power in the amplifying media.